Replace the IConfiguration parameter on AddInfrastructure() with a builder
that makes RabbitMQ wiring explicit and validated.
- Add MessagingServiceInfrastructureConfiguration exposing
AddRabbitMqConnectionFactory() with IConfiguration and Action<T> overloads
- EnsureRabbitMqConnectionFactoryAdded() throws at registration time if the
caller omits the wiring step
- Remove the implicit services.AddRabbitMqConnectionFactory(configuration)
call from AddInfrastructure(); callers must opt in via the builder
